Numerals denoting footnotes to various references including patents and other documents are provided in the following description of the related prior art. The references cited in the footnotes are listed in the Bibliography section of the specification immediately following Background of the Invention section.
Power devices have been widely used in many applications including inverters or converters for controlling motors, inverters for illumination, various power sources, and switches for driving solenoids and relays.sup.1-4. The power devices were conventionally driven and controlled by electronic circuits constructed as a combination of individual semiconductor devices and electronic components.sup.5,6. These functions have been more recently performed by low-voltage integrated circuits of several dozens of volts class.sup.7,8 or high voltage integrated circuits of several hundreds of volts.sup.9,10, which utilize recent LSI (large scale integration) technology. Power integrated circuits in which drive and control circuits and power devices are integrated on the same semiconductor substrate are also used to reduce the size of conversion devices, such as inverters or converters, and achieve high operating reliability thereof.sup.11,12.
FIG. 33 is a circuit diagram mainly showing a power-related portion of an inverter for controlling a motor. Power devices (Q1-Q6 as IGBTs--insulated gate bipolor transistor--and D1-D6 as diodes in this example) used for driving a three-phase motor form a bridge circuit, and are all stored in the same package to provide a power module.sup.13. The main power source V.sub.CC usually provides a high voltage of dc 100 to 400 volts. V.sub.CCH represents the high-potential side of the main power source V.sub.CC, and V.sub.CCL represents the low-potential side of the main power source V.sub.CC. To drive IGBTs Q1-Q3 connected to the V.sub.CCH, the potential of gate electrodes of the IGBTs Q1-Q3 needs to be higher than the V.sub.CCH. Accordingly, the drive circuit is provided with a photo coupler (PC) or a high voltage integrated circuit (HVIC). The input and output terminals (I/O) of the drive circuit are usually connected to a microcomputer adapted for controlling the inverter as a whole. FIG. 34 is a block diagram showing constituent units of the high voltage integrated circuit (HVIC) used in the circuit of FIG. 33. This circuit includes a control unit CU, gate drive units GDU and a level shift unit LSU. The control unit sends and receives signals to and from a microcomputer, through input and output terminals I/O, to generate control signals for turning on and off selected one(s) of the IGBTs. The gate drive units GDU 4-6 receive signals from the control circuit CU through input lines SIN 4-6 and generate signals to output lines OUT 4-6 for driving gates of the corresponding IGBTS. Each of the gate drive units GDU 4-6 also detects excessive current and heat of the IGBT with a current detecting terminal.sup.14 OC 4-6 and a temperature terminal.sup.15 OT 4-6, and generates abnormal signals through a corresponding output line SOUT 4-6. In this manner, the gate drive units GDU 4-6 drive corresponding IGBT Q4-Q6 connected to the low-potential side V.sub.CCL of the main power source V.sub.CC of FIG. 33. The gate drive units GDU1-GDU3 performs the same functions as the gate drive units GDU4-GDU6, to drive corresponding IGBT Q1 to Q3 that are connected to the high-potential side V.sub.CCH of the main power source V.sub.CC. The level shift unit LSU functions as an interface between the V.sub.CCL -level signals of the control circuit CU, and the signals (SIN 1-3, SOUT 1-3) of GDU 1-3 which fluctuate between the V.sub.CCH level and the V.sub.CCL level. Drive power sources (shown in FIG. 35) V.sub.DD1 -V.sub.DD3 for the GDU 1-3 have respective high-potential sides V.sub.DDH1 -V.sub.DDH3 and low-potential sides V.sub.DDL1 -V.sub.DDL3. The GDU 4-6 are connected to a common drive power source V.sub.DDC (not shown in FIG. 35), which has a high-potential side V.sub.DDHC and a low-potential side V.sub.DDLC. The common drive power source V.sub.DDC for the GDU 4-6 and CU is about 10 to 20V, and the low-potential side V.sub.DDLC of this common power source V.sub.DDC is connected to the low-potential side V.sub.CCL of the main power source V.sub.CC of FIG. 33.
FIG. 35 shows in more detail the connection between the GDU1 of FIG. 34 and the IGBT Q1. The other GDUs and IGBTs are not shown in this figure. The drive power source V.sub.DD1 of the GDU1 is about 10 to 20 volts. The low-potential side V.sub.DDL1 of this power source is connected to an emitter terminal of IGBT Q1, namely, a U phase of inverter output, and a collector terminal C of the IGBT Q1 is connected to the high-potential side V.sub.CCH of the main power source V.sub.CC. In this arrangement, when the IGBT Q1 is turned on, the potential of V.sub.DDL1 is made substantially equal to the potential of V.sub.CCH. When the IGBT Q1 is turned off, the potential of V.sub.DDL1 is made substantially equal to the potential of V.sub.CCL. Accordingly, the withstand voltage between the GDU1 and other circuit units needs to be higher than the voltage of the main power source V.sub.CC. This also applies to GDU2 and GDU3. Further, the level shift circuit LSU itself must have high withstand voltage. In FIG. 35, the IGBT Q1 includes a current detecting element.sup.16 M, a temperature detecting element .theta., and a temperature detecting terminal Temp. The gate drive unit GDU1 detects abnormal states of the IGBT Q1, through the current detecting terminal OC1 and the temperature detecting terminal OT1, and abnormal signals are generated through the output line SOUT 1. OUT 1 indicates a gate drive terminal.
FIG. 36 is a circuit diagram showing substantially the same circuit as that of FIG. 33, except the use of a product called "intelligent power module" .sup.18. In this case, the gate drive units GDU1-GDU6 consist of low voltage integrated circuits, individual electronic components and semiconductor devices, and are stored along with power devices (Q1-Q6, D1-D6) in a package containing the power devices. In this case, too, a photo coupler PC or high voltage integrated circuit HVIC is used as an exterior drive circuit.
FIG. 37 shows in detail the vicinity of IGBT Q1 and GDU1 of FIG. 36. SIN1 and SOUT1 are connected to the PC or HVIC provided outside of the power module.
To provide other structures, power IC technology for integrating the GDU1 and Q1 on one chip (on the same semiconductor substrate).sup.19,20, or power IC technology for integrating all the units of FIG. 36 in one chip.sup.11,12 can be employed.
FIG. 38 is a plan view showing a chip of the high voltage integrated circuit HVIC shown in FIG. 34, to clarify the arrangement of circuit units constituting the circuit. The GDU1 is formed in an island electrically separated from the other circuit units by junction separation.sup.21,22,10 or dielectric separation.sup.23,11,12 to assure high withstand voltage, and the periphery of this GDU1 is surrounded by a high voltage junction terminating structure HVJT.sup.11,21. The HVJT is a structure of a terminating part of the junction to which high voltage is applied to insulate the unit therein from the other units. Within the level shift circuit LSU, there is provided a high voltage n-channel MOSFET (HVN) adapted for shifting a level of signal having the potential V.sub.CCL on the low-potential side of the main power source V.sub.CC, to a level of signal (to be fed to the input line SIN1) having the potential V.sub.DDL1 on the low-potential side of the drive power source V.sub.DD1. This high voltage n-channel MOSFET is provided with a high voltage junction terminating structure.sup.10,11 HVJT surrounding a drain electrode D.sub.N at the center of the MOSFET. Within the island of the GDU1, there is provided a high voltage p channel MOSFET (HVP) adapted for shifting V.sub.DDL1 level of signals (received from the output line SOUT1), to V.sub.CCL level of signals. This high voltage p-channel MOSFET is also provided with a high voltage junction terminating structure HVJT surrounding a drain electrode D.sub.P at the center of the MOSFET. The input line SIN1 and output line SOUT1 of the GDU1 are installed to extend between GDU1 and LSU, over the high voltage junction terminating structure HVJT. Each of the GDUs is provided with an OUT terminal, OC terminal and OT terminal as shown in FIG. 35. GDU1-GDU3 are provided with respective V.sub.DDH1 -V.sub.DDH3 terminals, and V.sub.DDL -V.sub.DDL3 terminals, and GDU4-GDU6 are provided with V.sub.DDHC terminal and V.sub.DDLC terminal. In FIG. 38, the arrangements of these elements of the GDU1 and GDU4 are shown in detail, and those of the other GDUs are not shown.
Problems encountered in the conventional high voltage integrated circuit and power IC include the difficulty in providing high withstand voltage exceeding 600V, and high manufacturing cost. The problems will be described in more detail.
(1) Problems relating to separation techniques
As described above, separation techniques for electrically separating a circuit unit (e.g., GDU 1, 2, 3 shown in FIG. 38) having a greatly different potential from other units include dielectric separation.sup.11,12,13 junction separation.sup.10,21,22 and self separation.sup.20,24. The structures for enabling dielectric separation and junction separation, however, are complicated, and require high manufacturing cost. The manufacturing cost is further increased with an increase in the withstand voltage required. Although the manufacturing cost can be reduced by employing the self separation, technology has not been developed for achieving high withstand voltage in the structure of CMOS (complimentary MOSFET). In the structure of NMOS (n-channel MOSFET) capable of providing high withstand voltage, it is extremely difficult to achieve sufficiently high accuracy of analog circuits (i.e., the current detecting circuit and temperature detecting circuit as described above).
(2) Problems relating to high voltage junction terminating structure HVJT
Various kinds of high voltage junction terminating structures have been disclosed that include those for vertical power devices.sup.25,26, and those for lateral high voltage devices.sup.27,29. In the high voltage power IC in which the high voltage integrated circuit and power devices are integrated, however, high voltage junction terminating structures for many applications, such as those (surrounding GDU 1-3 in FIG. 38) formed between integrated circuit units, those (surrounding D.sub.N of HNN in FIG. 38) for high voltage lateral n-channel MOSFETs, those (surrounding D.sub.P of HVP in FIG. 39) for high voltage lateral p-channel MOSFETs, and those for vertical power devices, need to be formed on the same chip. With the conventional high voltage IC or power IC constructed for limited applications, many different kinds of high voltage junction terminating structures HVJT must be formed on the same chip, resulting in increased manufacturing cost.
(3) Problems relating to high voltage junction terminating structure on which wiring is provided
In the high voltage IC in which signals travel between integrated circuit units (e.g., GDU1 and LSU of FIG. 38) having greatly different potentials, wiring needs to be provided on the high voltage junction terminating structure HVJT. In this case, however, the high voltage junction terminating structure HVJT may be influenced by the potential of the wiring provided thereon, resulting in reduced withstand voltage of the HVJT, as in (30). Although various structures have been proposed to solve this problem.sup.10,11,12,31, these structures are complicated, and are only available at high manufacturing cost. Also, these proposed structures are not completely free from the influence of wiring, and is only able to prevent reduction of the withstand voltage to a limited extent. Thus, the known structures can provide the withstand voltage of up to about 600V, but cannot achieve higher withstand voltage.
It is therefore an object of the present invention to provide a high voltage integrated circuit at a reduced manufacturing cost, using inexpensive high voltage junction terminating structure having second and fourth regions for withstanding high voltage, which can be widely used as HVJT for vertical power devices, those for separating IC units from each other, and those for high voltage n-channel or p-channel lateral MOSFET, and which can maintain high withstand voltage even if wiring is provided thereon.